The present invention relates to a method and means for the manufacture of solid forging blocks with manipulator pins by filling an ingot provided with a borehole by the electro-slag remelt process with at least one consumable electrode. The ingot with the vertical borehole is placed on a block table with at least one power connection in the region of the block table and flush with a depression for the slag start material, and the filling of the core zone occurs starting at this depression.
In the manufacture of steel forging blocks there occrus the hazard, as the block diameter increases, that there may appear, in the core zone, structural defects which may lead to the rejection of the block involved. It is already known in the art how to perforate large-diameter ingots, removing the core zone, and to fill the resulting hollow space (cavity) in accordance with the initially described procedure by the electroslag process without defects (German Patent, No. 2,122,306 and German Laid-Open Document 2,403,843).
In the last-mentioned publication (2,403,843), in view of the starting phase of the known procedure, it is recommended that the bottom plate be provided with a recess in which the starting material, comprising metal shavings and slag, be placed and then ignited and molten by means of a permanent electrode. After a while, the recess is filled with liquid steel which is withdrawn from the perforated ingot. This results in a material loss, even though small, flawless block material is involved.
The recess in the bottom plate is extremely flat and extends also in the radial direction underneath the retained part of the ingot, forming dead corners in which unmolten slag is enclosed by the steel melt. The resulting extension is not only too small for a manipulator pin; its volume is not sufficient to accommodate all slag not molten during the cold start so that a part of the ingot base must be cut off and discarded before further processing. Then a new manipulator pin must be made by forging to facilitate further process of the ingot.
A major problem is the supply of the melting current to the perforated ingot. Its underside has considerable unevennesses and tinder layers which do not ensure sufficient melting current supply. Hence the melt parameters, in an extremely undesirable manner, are subject to great fluctuations which are detrimental to a homogeneous structure. The steel, first liquid and collecting in the recess of the bottom plate and then solidified, by itself would ensure good current transfer. However, this possibility is eliminated because the material in the recess, due to the solidification and cooling process, is subject to a strong cross- and lengthwise contraction so that the metallic contact in the recess, required for current transfer, is interrupted after a short time interval.
It is, therefore, an object of the present invention to provide a process and an apparatus by means of which, without additional measures, a manipulator pin can be produced on forging blocks during the manufacturing process, and by means of which a trouble-free transfer of the melting current during the starting phase and the subsequent remelt phase is made possible.